The invention relates to a grounding jack which is particularly useful in providing redundant grounding for a patient load center in hospitals and the like. When electrical equipment is used on a patient, suitable electrical receptacles are provided to furnish electric current to such equipment. Unless adequate grounding is provided for, there is always a danger to the patient. The regular U-blade plug provides ground to whatever equipment is being used, but it is customary and advisable to use a receptacle cluster as the patient load center, which has one or more grounding jacks for redundant grounding and which may be connected to the frame of the patient's bed or other metal furniture or to other equipment in the room. The jack is bussed together with the ground of the duplex receptacle so that there is a common ground and no potential voltage or current can follow a different path, such as through the patient.
Such grounding jacks comprise a female member which includes a current-carrying sleeve connected to ground, and a current-carrying male pin or plug to be inserted into the sleeve. The cable connected to the plug may then be attached to the bed frame or equipment. Interengaging parts on the plug and sleeve have been used for locking the parts together but this locking feature, heretofore, has been in the current-carrying parts of both the male and female members, so that if they become unlocked inadvertently or broken, no current will flow or at least much of the integrity of the current will be lost.
For example, the current-carrying plug had a radially extending locking pin which also carried current. The current-carrying sleeve had recesses therein, shaped to receive the locking pin and lock the two members in place by relative rotation thereof. A coiled compression spring within the sleeve exerted axial pressure on the plug to hold the parts together. Reliance was placed on the pin to carry the current and if the pin broke, little or no current could flow and because of the slip fit between the plug and sleeve, the parts could easily become separated and, therefore, dangerous to the patient.